A fuel tank made of plastics material is provided with a hydrocarbon barrier which prevents or limits hydrocarbon emissions through its wall, e.g. in the form of leaks or by diffusion.
Known barriers are obtained by fluorination methods or they are constituted by a layer of ethylene vinyl alcohol copolymer (EVOH) inserted between two layers of polyethylene.
Vessels made in this way generally give satisfaction in terms of the hydrocarbon emission criterion.
Nevertheless, they require various arrangements, in particular to enable them to be connected to ducts, e.g. for delivering or receiving liquid fuel, and also for allowing gas to flow in the fuel system.
It is therefore necessary for such vessels to be pierced in order to put ducts into communication with the inside thereof and to make assemblies by screwing, heat-sealing, snap-fastening, or other means in order to secure said ducts to the wall of the vessel.
Such piercing and assembly operations give rise to passages through the hydrocarbon barriers and they thus make hydrocarbon emissions possible.
French patent FR 2 459 121 describes a hollow body made by blowing, e.g. a motor vehicle tank, the hollow body including a piece of metal held captive in its wall, the captive piece having perforations into which a single layer material forming the hollow body penetrates while it is being blown, the captive piece being designed to co-operate with a stopper element.
The captive piece is thus retained very strongly in the wall of the hollow body.
German patent application DE-A-4 205 332 describes assembling a metal coupling element to a fuel tank made by blowing a single layer of material, in which the parison for forming the tank partially covers said coupling element.
Such an assembly serves to limit hydrocarbon emissions to some extent.